Why does my laptop battery die after 5 minutes with Ubuntu?

I’m new to Ubuntu but wanted to replace Windows 10 on my old laptop with something faster.

I’ve installed Ubuntu 18.04 and it’s going ok so far except that the battery dies after about 5 minutes when the laptop is unplugged.

After some research it seems like it might be a video driver issue. However, I don’t know how to find out if the correct driver is installed. My laptop is an Acer Aspire E1-571 with integrated graphics.

Can anyone help me diagnose this issue?